海水改性分子筛吸附剂脱除燃煤烟气中Hg0的实验研究

由于在吸附剂中引入卤族元素可以极大地促进其对燃煤烟气中Hg~0的脱除,考虑到海水中含有丰富的氯元素,因此采用海水改性来提高吸附剂脱除Hg~0的效率。在氧气体积分数为6%的氮氧(94%N_2+6%O_2)基本气氛下进行了改性吸附剂脱除Hg~0的活性测试。研究表明:经海水改性后提高了吸附剂的脱汞效率且改性吸附剂对Hg~0主要以化学吸附的方式脱除;改性吸附剂的最高脱汞效率达到90%,相比于Na(13X)分子筛原样的脱汞效率提升了约40%,表明通过海水改性来提高吸附剂脱汞效率是可行的。     

分级燃烧对固体吸附剂吸附痕量金属的影响

在一维煤粉燃烧炉实验研究了分级燃烧方式对吸附剂控制重金属元素排放的影响。试验发现分级燃烧会增加亚微米颗粒中重金属的浓度,不利于对痕量重金属元素的控制,尤其对挥发性大的元素(如Cu和Ni)影响越明显;固体吸附剂对煤中重金属的排放具有吸附作用,并且吸附剂对不同的重金属元素的吸附有选择性;最后对吸附剂吸附重金属元素的机理做了阐述,吸附剂吸附重金属元素是通过物理吸附和化学吸附,其中它们在吸附过程中是共存的。     

Study of thermal conductivity,permeability, and adsorption performance of consolidated composite activated carbon adsorbent for refrigeration

Composite adsorbents, comprising activated carbon and expanded natural graphite, have been developed, and their thermal conductivity, permeability and adsorption performance were tested. The thermal conductivity varied with the ratio of activated carbon to expanded natural graphite. Thermal conductivity increased as the ratio of expanded graphite increased. Considering that the density of activated carbon for the composite adsorbent should not be lower than 200 kg/m³, otherwise the volumetric cooling capacity would be unacceptably low, the highest thermal conductivity obtained from experiments was 2.47 W m^?1 K^?1. The permeability was also measured, and the best result obtained was 4.378 × 10^?12 m². In order to evaluate the influence of heat and mass transfer on adsorption performance, the adsorption rate was tested using a Rubotherm magnetic suspension balance, and results showed that for the freezing conditions lower than ?10 °C the performance of granular activated carbon was better than that of solidified adsorbent because of the reduced mass transfer of ammonia at low saturated pressure. The adsorption performance of consolidated adsorbents increased rapidly when the evaporating temperature was higher than ?10 °C. When the evaporating temperature was 8 °C, the adsorption rate of consolidated adsorbent was improved by 29% if compared with that of granular adsorbent.     

An ideal visible nanocomposite (Fe/GTiP) photoanode catalyst for treatment of antibiotics in water and simultaneous electricity generation in the photocatalytic fuel cell

The photocatalytic fuel cell (PFC) has been studied for the wastewater treatment and electricity generation by degrading antibiotic organic pollutant berberine chloride (BC). Through a simple chemical process Fe/GTiP anode and ZnIn₂S₄ cathode catalysts were prepared and loaded them on carbon fiber cloth. Up to 79% BC (10 mg/L) was removed with simultaneous electricity generation of 0.65 V within 90 min under pH-7 in PFC by using visible light (two 50-W halogen lamps). PFC is better with 79% BC removal and electricity generation than only 79% removal in photocatalysis (PC) without generating any clean energy. Under photocatalysis Fe/GTiP can remove 70% of BC, higher than 54% with GTiP and 12% with TiP at 50 mg catalyst/50 mL (10 mg/L BC). The photocatalytic performance of Fe/GTiP was also compared with commercial P25 and pure TiO_2. The obtained removal of 17.4% and 13.25% BC (10 mg/L) with P25 and TiO₂ proves that with more visible light absorption Fe/GTiP has significant photocatalytic effect than P25 and pure TiO₂. The impacts of external resistance, concentration of catalyst, pH, and electrolyte were investigated in the PFC. Removal of tetracycline hydrochloride (TC) (10 mg/L) followed the same trend as BC under photocatalysis with Fe/GTiP, GTiP and TiP (78%, 60% and 33% at pH-7). The removal of 89% TC (30 mg/L) in 90 min was also achieved with Fe/GTiP. The experimental study shows that Fe/GTiP visible light nanocomposite is ideal for removing antibiotics in water by photocatalysis or with simultaneous electricity generation through PFC.     

Microbial fuel cell (MFC)-based biosensor for combined heavy metals monitoring and associated bioelectrochemical process

To explore the feasibility and related mechanism of MFC biosensor for wastewater detection under the action of combined heavy metals. Cyclic voltammetry (CV) and scanning electrochemical impedance spectroscopy (EIS) were used to explore the related bioelectrochemical process. The response of the reactor to single/combined heavy metals, low/high heavy metal concentrations, and the differences in ohmic resistance (Rs) and charge transfer resistance (Rct) were investigated using Ni as the core heavy metal and the combined action of Cd, Cu and Zn. The results indicated that there was a linear relationship between the concentration and output voltage of the MFC biosensor under the action of combined heavy metals (R² = 0.8803–0.973). However, the internal resistance (Rint) of the MFC biosensor under the action of single heavy metal was far less than that of the combined heavy metal group, and the power density (19.849 W m^?3) was 4 times that of the combined heavy metal group (3.109–4.589 W m^?3). The Rs of the biosensors in the combined heavy metal group were 0.868Ω and 0.860, which were higher than 0.768Ω of the single heavy metal sensor. With the increase of the concentration of heavy metals in the influent, the increase of Rct was more obvious in the combined group, while the Rs in the single group significantly increased (P < 0.05). The results imply that it is possible for MFC biosensors to be used in the detection of actual water polluted by various heavy metals, but the biosensor performance is mainly limited by Rct, which needs to be further improved.     

Use of adsorbents for thermal energy storage of solar or excess heat: improvement of energy density

The current paper describes the design of a prototype system to explore the feasibility of the adsorption thermal energy storage. Water was chosen as the adsorbate, and three different adsorbents were tested. Zeolite 13X, NaLSX zeolite, and an activated alumina (AA)/zeolite 13X composite adsorbent were used as adsorbents. Experiments were performed at varying flow rates and different relative humidities to determine the optimal operating conditions for the system. The regeneration of the adsorbents also was explored by performing repeated runs on the same adsorbent sample. The results indicate that complete regeneration was achieved. A maximum energy density of 160 kWh/m³ has been achieved with the AA/13X adsorbent, and this adsorbent was chosen for further studies. After this adsorbent screening, the system was modified to improve the data recording and system performance. Tests were performed on AA/13X, and a maximum energy density of 200 kWh/m³ was achieved, which was much higher than the maximum energy density reported in the literature for adsorption thermal energy storage systems (165 kWh/m³). Copyright © 2012 John Wiley & Sons, Ltd.     

A review on the utilization of fly ash

Fly ash, generated during the combustion of coal for energy production, is an industrial by-product which is recognized as an environmental pollutant. Because of the environmental problems presented by the fly ash, considerable research has been undertaken on the subject worldwide. In this paper, the utilization of fly ash in construction, as a low-cost adsorbent for the removal of organic compounds, flue gas and metals, light weight aggregate, mine back fill, road sub-base, and zeolite synthesis is discussed. A considerable amount of research has been conducted using fly ash for adsorption of NO_x, SO_x, organic compounds, and mercury in air, dyes and other organic compounds in waters. It is found that fly ash is a promising adsorbent for the removal of various pollutants. The adsorption capacity of fly ash may be increased after chemical and physical activation. It was also found that fly ash has good potential for use in the construction industry. The conversion of fly ash into zeolites has many applications such as ion exchange, molecular sieves, and adsorbents. Converting fly ash into zeolites not only alleviates the disposal problem but also converts a waste material into a marketable commodity. Investigations also revealed that the unburned carbon component in fly ash plays an important role in its adsorption capacity. Future research in these areas is also discussed.     

Permeability and thermal conductivity of compact chemical and physical adsorbents with expanded natural graphite as host matrix

Permeability and thermal conductivity test units were designed to study the heat and mass transfer performance of compact chemical and physical adsorbents, i.e. compact CaCl₂ and activated carbon (AC) using expanded natural graphite (ENG) as host matrix. The thermal conductivity was studied by steady-state heat source method and the permeability was tested with nitrogen as a gas source. For the compact CaCl₂ adsorbents, results show that permeability and thermal conductivity vary with the ratio of ENG and the density of compact adsorbents. The value of permeability is 10^-13 ～ 10^-11 m² when the density of compact sample change from 400 kg/m³ to 550 kg/m³, and it keeps increasing linearly with the less ratio of ENG. The value of thermal conductivity is 1.08 W/(m·K), which is increased by 5 times compared with granular CaCl₂ when the density is 550 kg/m³ and the ratio of ENG is the minimum value of 16.7%. The compact physical adsorbent of AC with ENG as matrix has the highest thermal conductivity of 2.61 W/(m·K) when the ratio between ENG–AC is 1.5:1. Similarly, thermal conductivity drops down with the ratio of ENG decreasing. When the ratio of ENG reaches the minimum ratio of 28.6%, the thermal conductivity is 2.08 W/(m·K), which is increased by 5.8 times if compared with the result of granular AC, and corresponding permeability is 5.16 × 10^-11 m². The thermal conductivity and permeability of compact physical adsorbent of AC are all better than the values for the compact chemical adsorbent of CaCl₂.     

FeMoO4-graphene oxide photo-electro-catalyst for berberine removal and hydrogen evolution

Photo-electro-catalytic degradation of antibiotics such as berberine in water with simultaneous hydrogen evolution is an attractive option. It can control pollution using solar energy and provide clean energy. The photo electrodes play vital role in this kind of photocatalytic electrolytic cell. To obtain better electrode with high degradation capacity and fast hydrogen generation rate, using a facile one-pot hydrothermal process, a series of nano-structured composite FeMoO₄-GO (graphene oxide) catalysts with improved absorbance in 250–800 nm were synthesized, and loaded on CFC (carbon fiber cloth). Their photo electrode performance were compared. Using SEM(scanning electron microscope), XRD (X-ray diffraction) and XPS(X-ray photoelectron spectroscopy), the catalysts were characterized, and LSV(linear sweep voltammetry), CV(cyclic voltammetry) and EIS(electrochemical impedance) were used to characterize the electrodes. In 1 M KCl supporting electrolyte, at current density 10 mA cm⁻², 90% berberine was removed in 30 min and hydrogen generation rate was 3.1 μmol cm⁻² min⁻¹ in photo-electro-catalysis system. The results show rapid hydrogen generation and enhanced pollutant degradation.     

Development research on composite adsorbents applied in adsorption heat pump

A novel adsorbent design technique base on the concept of Kelvin equation was proposed to develop hydrophilic adsorbent applicable to water vapor adsorption heat pump (AHP) for high performance. In the process, the composite adsorbent was prepared after silica gel was synthesized in the pores of activated carbons by impregnating activated carbons in sodium silicate solution. Two kinds of activated carbons were tested to produce composite adsorbent and to investigate the performance by measuring the adsorption isotherms of water vapor and pore structure characteristics. All adsorption isotherms of the silica impregnated activated carbons prepared shifted to a lower region of water vapor pressure compared to those of the raw activated carbons. The volume-based amount of adsorption in the AHP operation range (φ = 0.1–0.4) for the adsorbents prepared at sodium silicate solution concentration of 10 wt.% and impregnating time of 48 h are 5.88 and 2.62 times that of the raw activated carbons (AC1 and AC2), respectively. Based on the Kelvin equation, it is clarified that the contact angle and the volume of pore radius greater than 1.2 nm decrease with the increase of sodium silicate solution concentration for the novel composite adsorbents, which contributes the isothermals shift to lower relative pressure range.     

The adsorption refrigeration characteristics of alkaline-earth metal chlorides and its composite adsorbents

A study was conducted on the adsorption characteristics of the adsorption refrigeration working pairs using alkaline-earth metal chlorides as adsorbents and ammonia as refrigerant. The adsorption isotherms between alkaline-earth metal chlorides and nitrogen were studied. The study shows that the adsorbents of CaCl₂, SrCl₂ provide better adsorption capability associated with ammonia when compared to that of MgCl₂, BaCl₂. CaSO₄ was added into the CaCl₂, SrCl₂ with a mass ratio 20%, respectively, in order to solve the swelling and smashing problems encountered with CaCl₂, SrCl₂ adsorbent particles. The adsorption refrigeration experiments of composite adsorbents were investigated. The results show that the refrigeration capacity of the unit adsorbent of CaCl₂/CaSO₄ is 1.26 times higher than that of CaCl₂, and SrCl₂/CaSO₄ is 1.6 times higher than that of SrCl₂ at 100 °C. The mechanism of NH₃ adsorption and the gelatification of CaSO₄ were also discussed. BET (Brunauer–Emmett–Teller) specific surface area and pore structure of adsorbents were examined. Results show that the BET specific surface area and pore structure of composite adsorbents are retained well. This study indicates that the refrigeration capacity could be enhanced by compositing the adsorbents which indicates that composite adsorbents can perform better in adsorption refrigeration, and can be employed in adsorption refrigeration system using low-grade heat source.     

Impregnated carbon–ionic liquid as innovative adsorbent for H2/CO2 separation from biohydrogen

Currently, purification is a considerably important technology for biohydrogen (bioH₂) production as a renewable energy resource. Adsorption methods are promising techniques for separation of CO₂ from the H₂/CO₂ mixture of bioH₂. In this study, the adsorbent is synthesized by impregnating activated carbon (AC) with ionic liquid (IL). The ILs were prepared using choline chloride and zinc chloride at different wt% with the AC, i.e., 0.5 wt%–3 wt%. The physical and chemical properties of the synthesized adsorbents, such as surface morphology, porosity, and structures, were investigated and characterized by using scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and Brunauer–Emmett–Teller analysis (BET). To investigate the actual adsorption performances, the effects of different synthesized adsorbent types and feed gas flow rates, i.e., 0.1–1.0 L min⁻¹, were observed. Hence, a commercial gas composed of CO₂ and H₂ mixture with different compositions, i.e., 40, 50, and 60 vol%, was used as synthetic bioH₂ gas. The adsorption capacity of CO₂, i.e., adsorption capacity, were determined using single adsorber column (0.6 L) at a temperature of 300 K and pressure of 1 bar. Results showed that adsorption capacity decreased with the increased feed gas flow rate. Moreover, the carbon impregnated with 1 wt% of IL showed the most excellent adsorption capacity at 84.89 mg of CO₂/g of adsorbent. The present results are the initial findings generated for the bioH₂ separation technology for future high-purity hydrogen production.     

Life cycle assessment of two palm oil production systems

In 2009 approx. 40 Mt of palm oil were produced globally. Growing demand for palm oil is driven by an increasing human population as well as subsidies for biodiesel and is likely to increase further in coming years. The production of 1 t crude palm oil requires 5 t of fresh fruit bunches (FFB). On average processing of 1 t FFB in palm oil mills generates 0.23 t empty fruit bunches (EFB) and 0.65 t palm oil mill effluents (POME) as residues. In this study it is assumed that land use change does not occur. In order to estimate the environmental impacts of palm oil production a worst and a best case scenario are assessed and compared in the present study using 1000 kg of FFB as functional unit.The production and treatment of one t FFB causes more than 460 kg CO_2eq in the worst case scenario and 110 kg CO_2eq in the best case scenario. The significant greenhouse gas (GHG) emission reduction is achieved by co-composting residues of the palm oil mill. Thus treating those residues appropriately is paramount for reducing environmental impacts particularly global warming potential (GWP) and eutrophication potential (EP).Another important contributor to the EP but also to the human toxicity potential (HTP) is the biomass powered combined heat and power (CHP) plant of palm oil mills. Frequently CHP plants of palm oil mills operate without flue gas cleaning. The CHP plant emits heavy metals and nitrogen oxides and these account for 93% of the HTP of the advanced palm oil production system, of which heavy metal emissions to air are responsible for 79%. The exact emission reduction potential from CHP plants could not be quantified due to existing data gaps, but it is apparent that cleaning the exhaust gas would reduce eutrophication, acidification and toxicity considerably.     

Measurement of physical and transport properties of tannery effluent (soak liquor)

Treatment of effluents is a serious issue for present process industries. Several new techniques are being developed which require the knowledge of effluent physical and transport properties for design and development of treatment plants. In this work density, kinematic viscosity, thermal conductivity and specific heat capacity of the tannery effluent (soak liquor) were measured for various salt concentrations of soak liquor ranging from 3% to 20%. A non-linear regression analysis has been carried out using these experimental data and the empirical correlations are presented.     

Porous reduced-graphene oxide supported hollow titania (rGO/TiO2) as an effective catalyst for upgrading electromethanogenesis

Microbial electrochemical system (MES) for enhancing methane production has gained significant interest during the recent years, but the practical applications of MES are still far away due to several limitations such as low efficiency of cathodic electrochemical kinetics. In this study, novel porous reduced-graphene oxide/hollow titania (rGO/TiO₂) was successfully synthesized to be used as cathode catalyst for promoting electrochemical reduction of CO₂ to methane. The MES operation with rGO/TiO₂ catalyst exhibited 15.4% higher methane yield (0.383 ± 0.01 LCH₄/gCOD) and 13.4% higher production rate (152.38 mL/L.d) compared to control MES with bare carbon cloth cathode. The MES-rGO/TiO₂ produced around 33% higher in total Coulomb at 3837.9 ± 351.5C compared to the pristine cathode at 2887.92 ± 254.6C. Substrate degradation and volatile fatty acids conversion were significantly improved in the presence of rGO/TiO₂ catalyst. By using cyclic voltammetry and electrochemical impedance spectroscopy analysis, rGO/TiO₂ was proved to ease the electron transfer efficiency of working cathode for the conversion of electron to methane. The results suggest that porous rGO/TiO₂ can be a promising cathode catalyst to upgrade the performance of a scalable methane-producing MES-AD system.     

Recent Studies on Activated Carbons and Fly Ashes from Turkish Resources

This article deals with adsorptive properties of activated carbons (ACs) and fly ashes from Turkish coal and biomass resources. ACs because of their high surface area, microporous character and the chemical nature of their surface have been considered potential adsorbents for the removal of heavy metals from industrial wastewater. Pyrolysis is an established process method for preparation of activated carbon from biomass. The bio-char is can be used as AC. The adsorption properties of ACs were strictly defined by the physicochemical nature of their surface and their texture, i.e., pore volume, pore size distribution, surface area. It is well known that the pH of the solution-adsorbant mixture is an important variable in the adsorption process. Fly ash has the highest adsorption capacity (198.2 mg/g) for Cd(II). Almond shell AC has the lowest adsorption capacity (2.7 mg/g).     

PtIr alloy nanowire assembly on carbon cloth as advanced anode catalysts for methanol oxidation

The interconnecred PtIr alloy nanowires were uniformly deposited on carbon cloth via One-step wet chemistry method, which diameter is averaged to be 5 nm with a length of 50–200 nm. The carbon cloth supported PtIr nanowire assembly (PtIr NA/CC) shows a larger electrochemical active surface area (ECSA) due to its 3D nanostructure and a high CO-resistance as a result from the synergistic effect of PtIr alloy. The PtIr NA/CC exhibits an extremely high mass activity and a reliable long-term stability toward methanol oxidation reaction (MOR). The superior catalytic performance on MOR can match and even surpass those best Pt-based nanowires reported recently in the literature.     

Integrated bio-electrogenic process for bioelectricity production and cathodic nutrient recovery from azo dye wastewater

Microbial electrochemical treatment (MET) process was designed to evaluate complete mineralization of partially treated dye effluent obtained from anoxically operated Periodic discontinuous batch reactor (PDBR) for simultaneous bioelectricity generation and recovery of nutrients. In MET bioreactor, anode and cathode chambers were fed with designed synthetic wastewater (DSW) and PDBR dye effluents. The dye metabolite (NH₄⁺) will be converted to nitrates by the activity of aerobic biocatalyst present in cathode chamber to be used as biofertilizer. Dye removal of 90.2% was observed with good electrogenic activity (voltage (OCV)/current; 395 mV/1.77 mA). The mineralization of dye and its intermediates were assessed by reduction in overall toxicity from 23% to 4%. Chemical oxygen demand (COD) removal efficiency of 75% (anode) and 88% (cathode) were observed in correspondence to higher azoreductase (18.7 U; 48 h) and dehydrogenase (1.66 μg/ml of toluene; 24 h) enzyme activities which correlated well with metabolic activities of biocatalyst. Bioelectrocatalytic behavior of mixed biocatalyst on the basis of redox catalytic currents and prevalence of redox mediators signified the specific function of electron transfer toward dye mineralization. The results obtained suggest that the use of MET can considerably degrade toxic pollutants and provides nitrate rich solution (biofertilizer). Utilization of recovered nutrients directly to farms without any energy intensive methods is reported in this communication.     

C-O-Co bond-stabilized CoP on carbon cloth toward hydrogen evolution reaction

Highly active, low-cost, and durable electrocatalysts toward hydrogen evolution reaction (HER) are crucial for electrochemical water splitting. Herein, a green, facial, and effective strategy was proposed to develop CoP on carbon cloth (CoP/o-CC) as efficient self-supported hydrogen evolution electrodes. The designed CoP/o-CC exhibits superior catalytic activity with overpotentials of 118 mV and 95.45 mV to deliver a current density of 10 mA cm^?2 in acidic and alkaline solution, respectively, which is superior to most reported studies. In addition, the designed CoP/o-CC electrode also possesses excellent stability even under a large current density of 100 mA cm^?2. The origin of significantly enhanced stability thereby was further systematically investigated. Experimental study reveals that the oxygenated functional groups on carbon cloth play the role to bind the CoP electrocatalysts, forming C-O-Co bonds. Thus, the enhanced electrochemical and structural stability of CoP/o-CC is predominantly caused by the interfacial interaction of the C-O-Co bonds between the CoP active materials and surface oxygenated functional groups of carbon fiber. Therefore, we believe that this work provides an in-depth insight into the role of interfacial interaction between the substrate and the catalysts and offers a new methodology to design durable and efficient electrocatalysts.     

Release of inorganic trace elements during gasification of wood,straw, and miscanthus

The release of alkali metals, chlorine, sulphur and heavy metals during gasification of four different types of biomass was investigated. The samples were two types of wood (clean and waste wood), miscanthus, and straw. Experiments were conducted in two different setups; in a tube furnace which could be considered as batch experiments, and in an atmospheric lab scale fluidised bed reactor with continuous fuel feed. Molecular beam mass spectrometry was used for on-line analysis of the hot gas. The experimental results reveal that the release of inorganic species like HCl, KCl and H₂S is strongly dependent on other inorganic constituents in the samples, e.g. Si and Ca. In general, the release from herbaceous biomass is much higher than from woody biomass. With the exception of zinc released from miscanthus at temperatures above 900 °C, no heavy metals could be detected. The measurements were accompanied by equilibrium calculations using FactSage 5.5 and the FACT database which are in relatively good agreement with the experimental results.